1. Field of the Invention
The present invention relates to a control circuit for an optical transmitter/receiver that transmits an operating condition of the optical transmitter/receiver to an outside host apparatus, and more particularly, to a control circuit for an optical transmitter/receiver capable of saving an amount of memory.
2. Background Art
Optical transmitters/receivers that transmit/receive optical signals are widely used in optical communications using optical fiber or the like. There is a proposal of a control circuit for such an optical transmitter/receiver having a monitoring function that transmits an operating condition of the optical transmitter/receiver to an outside host apparatus (e.g., see Patent Document 1: Japanese Patent No. 3822861).
Optical transmitters/receivers are designed based on an industry standard called “Multi-Source Agreement” represented by XFP and SFP. Since products whose externally viewed interfaces and functions are standardized compete with each other on the market, these optical transmitters/receivers are extremely cost-sensitive. Furthermore, a hard wired microcontroller may be used as a control circuit for such an optical transmitter/receiver. The cost of this microcontroller tends to increase as the amount of memory mounted increases, and therefore it is necessary to use a microcontroller having the smallest possible amount of memory.
The control circuit for an optical transmitter/receiver in Patent Document 1 secures in a memory not only an area that stores an operating condition and a predetermined limit value of the optical transmitter/receiver but also an area that stores a flag produced when the operating condition exceeds the limit value. For this reason, there is a problem that as the number of parameters to be monitored such as temperature, bias, supply voltage, power of optical output, light-receiving power of the optical transmitter/receiver increases, both the necessary amount of memory and the cost increase.
Furthermore, in the case where the optical transmitter/receiver is provided with a function of reporting “Warning” when the operating condition exceeds a first limit value and “Alarm” when the operating condition exceeds a next second limit value, it is necessary to secure memory areas for five items of the operating condition, first limit value, second limit value, Warning flag and Alarm flag, which results in a problem that the amount of memory further increases.